As a final experiment, binding studies were carried out with bupivacaine (Figure 7-1) on

nanoparticle samples MIP4, MIPS, and MIP6 mOlecularly imprinted with amitriptyline.

Bupivacaine (pKa = 8.1) is an amide class local anesthetic used in clinical medicine to provide

local or regional anesthesia during surgical procedures, and the necessity in reducing quickly the

free concentration of bupivacaine has also recently attracted much attention.49 The uptake

experiments presented in Figure 7-8 and the partition coefficients provided in the figure captions

confirmed, in the absence of specific imprinting, that the uptake is mainly driven by hydrophobic

interactions, with the nanocapsule samples containing polar carboxylic acid groups binding less

efficiently bupivacaine molecules.


 40

 30 30




 MIP,


 0 10 20 30
 Nanoparticle amount (mg)

Figure 7-8. Uptake of bupivacaine by the nanoparticles molecularly imprinted with amitriptyline:
 MIP4 (K, ~ 190), MIPS (K, ~ 120), and MIP6 (K, ~ 120). The lines are provided to
 highlight the trends.

 7.3 Conclusions

 We demonstrated in this chapter that molecularly imprinted nanoparticles prepared by

simple miniemulsion polymerization can efficiently encapsulate large amounts of hydrophobic

toxic drugs such as amitriptyline or bupivacaine. The absence of template molecules during

nanoparticle synthesis prevents the formation of specific binding sites, and as a consequence the

uptake remains mainly driven by non-specific adsorption onto the nanoparticles through